Historically, 0-10V dimming signals for controlling light intensity have been transmitted over wires in cables that are part of and rated for a National Electrical Code (NEC) class 2 circuit. A class 2 circuit has sufficiently low voltage and current limitations such that the cables in the circuit do not have to be housed in raceway and conduit when they traverse the surface of a building. An NEC class 1 circuit can carry higher voltages and current, but the cables in such a circuit must be housed in raceway or conduit when they traverse the surface of a building. While different cables for different class 1 circuits can be routed together through common raceway and conduit, class 1 and class 2 circuits must be isolated from each other.
Recently, electrical cable manufacturers have started offering cables for use in NEC class 1 circuits that include power wires for transmitting line power 110-120V AC as well as low-voltage wires for transmitting a 0-10V dimming signal. The overall cable is rated for use in class 1 circuits.
Controllers for lighting control systems such as The Watt Stopper Inc.'s Digital Lighting Management system typically include inputs for line power and one or more sensors, such as occupancy and vacancy sensors. The line power is connected to one or more outputs for lighting loads within the controller through internal relays so that the lighting loads can be turned on or off based upon the status of the sensors. The controllers also typically include an output for a 0-10V dimming signal. The output is typically only suitable for a connection to a cable that is part of a class 2 circuit.